How to upgrade Ubuntu 15.10 32 bit to Ubuntu 20.04 64 bit?

What happens if you execute

sudo do-release-upgrade

?

Due to the fact that Ubuntu 15.10 is not supported any more, you may have to apply some additional steps, see e.g. https://help.ubuntu.com/community/EOLUpgrades

Maybe creating backup copies of your private files, doing a clean new installation of Ubuntu 20.04 and then restoring the files from the backup is easier.

Sir,

(1).
On executing “ sudo do-release-upgrade “, the OUT PUT comes as under:

navin@navin:~$ sudo do-release-upgrade
[sudo] password for navin:
Checking for a new Ubuntu release
Your Ubuntu release is not supported anymore.
For upgrade information, please visit:
http://www.ubuntu.com/releaseendoflife

Get:1 Upgrade tool signature [819 B]
Get:2 Upgrade tool [1,254 kB]
Fetched 1,255 kB in 0s (0 B/s)
authenticate 'xenial.tar.gz' against 'xenial.tar.gz.gpg'
extracting 'xenial.tar.gz'

Reading cache

Checking package manager
Reading package lists... Done
Building dependency tree
Reading state information... Done
Ign http://mirror.nus.edu.sg wily InRelease
Ign http://mirror.nus.edu.sg wily-updates InRelease
Hit http://ppa.launchpad.net wily InRelease
Ign http://mirror.nus.edu.sg wily-security InRelease
Ign http://mirror.nus.edu.sg wily-proposed InRelease
Ign http://mirror.nus.edu.sg wily-backports InRelease
Ign http://mirror.nus.edu.sg wily Release.gpg
Hit http://ppa.launchpad.net wily InRelease
Ign http://mirror.nus.edu.sg wily-updates Release.gpg
Ign http://mirror.nus.edu.sg wily-security Release.gpg
Ign http://mirror.nus.edu.sg wily-proposed Release.gpg
Ign http://mirror.nus.edu.sg wily-backports Release.gpg
Ign http://mirror.nus.edu.sg wily Release
Hit http://ppa.launchpad.net wily InRelease
Ign http://mirror.nus.edu.sg wily-updates Release
Ign http://mirror.nus.edu.sg wily-security Release
Ign http://mirror.nus.edu.sg wily-proposed Release
Ign http://mirror.nus.edu.sg wily-backports Release
Hit http://ppa.launchpad.net wily/main i386 Packages
Ign http://mirror.nus.edu.sg wily/main i386 Packages/DiffIndex
Ign http://mirror.nus.edu.sg wily/restricted i386 Packages/DiffIndex
Ign http://mirror.nus.edu.sg wily/multiverse i386 Packages/DiffIndex
Ign http://mirror.nus.edu.sg wily/universe i386 Packages/DiffIndex
Hit http://ppa.launchpad.net wily/main Translation-en
Err http://mirror.nus.edu.sg wily/main Translation-en

Err http://mirror.nus.edu.sg wily/multiverse Translation-en

Err http://mirror.nus.edu.sg wily/restricted Translation-en
.
.
.
.
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Like this all …..E R R O R S ………… as a very long list
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.
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Err http://mirror.nus.edu.sg wily-backports/restricted i386 Packages
  404 Not Found
Fetched 0 B in 6s (0 B/s)
Reading package lists... Done
Building dependency tree
Reading state information... Done

Updating repository information

No valid mirror found

While scanning your repository information no mirror entry for the
upgrade was found. This can happen if you run an internal mirror or
if the mirror information is out of date.

Do you want to rewrite your 'sources.list' file anyway? If you choose
'Yes' here it will update all 'wily' to 'xenial' entries.
If you select 'No' the upgrade will cancel.

Continue [yN]
.
.
.
and on giving YES nothing is coming out as fruitful output! All ERRORS as above and finally concludes as under:

, E:Some index files failed to download. They have been ignored, or
old ones used instead.

Restoring original system state

Aborting
Reading package lists... Done
Building dependency tree
Reading state information... Done
navin@navin:~$

(2).
It is true that Ubuntu 15.10 is not supported any more. So as suggested by you (under referencefor EOL), I applied additional steps. No positive result.

Please guide further.

Regards.
Navin Talati / 11-01-2021

Wipe the install off and do a clean install of Focal (Ubuntu 20.04). To upgrade from 15.04 you will need to upgrade ro 15.10 using a CD, then upgrade to 16.04 using the web. Then from 16.04 upgrade to 18.04 using the web, then use the web yet again to upgrade to 20.04

This will take absolutely ages and I doubt you'll have a happy OS with all the cruft from the old applications

A clean install will get you to where you want to be in one jump and feel like a new OS. You can restore your use files (Images / videos / music / whatever) from your backups. This will give you a cleaner OS and faster

"I applied additional steps. No positive result."
It seems that you didn't apply the important additional step (changing the repository server to "old-releases.ubuntu.com")

BUT:
It is irrelevant, because there is no i386 (=32bit) version of Ubuntu 20.04 any more, just an amd64 (=64bit) version, and there is no possibility to upgrade from your current 32bit version to a 64bit version.

This requires a new install in any case.

Thanks Sirs for #3 & #4.

You are right the ONLY fresh install will be the best and probably even possible. So I will follow that route only.

My existing O.S. (Ubuntu 15.10) is on a HDD having 3 partitions. TWO (2 nd & 3 rd) of them are of DATA only. On ONE (1 st) is occupied by the O.S.

As far as I remember, the OS is installed along /boot, /, /home and Swap internal partitions.

Could you please guide me how safely can I install a Fresh 20.04 LTS in that without touching DATA partitions?

Thanks.
Navin Talati / 12-01-2021

When installing a new Ubuntu system you will be asked how to format the hard disk (e.g. delete everything and use the full disk).
If you want to preserve the current /home, /boot and swap partitions, you have to select "something else" in that dialogue and then manually re-allocate the existing partitions in the same way as they currently are.

Due to the fact that any wrong key press (or mouse click) can lead to data loss, I strongly recommend creating backup copies of all your useful files to another medium, to enable restoring in case that something goes wrong.

As per the guidance in #6 and #7, the fresh installation of the Ubuntu 20.04 LTS could be installed without disturbing data partitions in the same hard drive.
Thanks.

Thanks actionparsnip, that solved my question.